U.S. patent number 4,864,010 [Application Number 07/205,141] was granted by the patent office on 1989-09-05 for monomers, oligomers, and polymers of biscyclobutarenes bridged by at least one benzoxazole linkage.
This patent grant is currently assigned to The Dow Chemical Company. Invention is credited to William J. Harris, Norman L. Madison, Alan K. Schrock.
United States Patent |
4,864,010 |
Schrock , et al. |
September 5, 1989 |
**Please see images for:
( Certificate of Correction ) ** |
Monomers, oligomers, and polymers of biscyclobutarenes bridged by
at least one benzoxazole linkage
Abstract
A biscyclobutarene monomer is prepared comprising two
cyclobutarene moieties bridged by a divalent radical having at
least one benzoxazole linkage. A reactive biscyclobutarene oligomer
is also prepared by reacting a cyclobutarene-carboxylic acid, a
diaminodihydroxyarene, and either an aromatic diacid or an aromatic
diacid chloride. The monomers and reactive oligomers can be
polymerized to form polymers exhibiting outstanding thermooxidative
stability at high temperatures for prolonged time periods.
Inventors: |
Schrock; Alan K. (Lake Jackson,
TX), Harris; William J. (Midland, MI), Madison; Norman
L. (Midland, MI) |
Assignee: |
The Dow Chemical Company
(Midland, MI)
|
Family
ID: |
22760978 |
Appl.
No.: |
07/205,141 |
Filed: |
June 9, 1988 |
Current U.S.
Class: |
528/185; 548/218;
528/176; 548/217; 528/183; 548/219; 548/220; 548/577 |
Current CPC
Class: |
C07D
263/57 (20130101); C08F 34/02 (20130101); C08G
61/00 (20130101) |
Current International
Class: |
C07D
263/00 (20060101); C07D 263/57 (20060101); C07D
519/00 (20060101); C08G 61/00 (20060101); C08F
34/00 (20060101); C08F 34/02 (20060101); C07D
498/00 (20060101); C07D 498/04 (20060101); C08F
038/00 (); C08F 132/08 () |
Field of
Search: |
;528/176,183,185
;548/217,577 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Denny et al., Polymer Preprints, vol. 29, No. 1, pp. 194-195 (Jun.
1988), entitled, "High Temperature Bisbenzocyclobutene (BCB)
Terminated Resin Properties". .
U.S. Ser. No. 883,240 to Kirchhoff dated Jul. 1986. .
U.S. Ser. No. 132,734 to Schrock dated Dec. 1986..
|
Primary Examiner: Anderson; Harold D.
Assistant Examiner: Mason; T.
Attorney, Agent or Firm: Goodwin; Matthew S.
Government Interests
The U.S. Government has a paid-up license in this invention and the
right in limited circumstances to require the patent owner to
license others on reasonable terms as provided for by the terms of
Contract No. F33615-85-C-5092 awarded by Wright-Patterson Air Force
Base.
Claims
What is claimed is:
1. A biscyclobutarene monomer comprising two cyclobutarene moieties
bridged by a divalent radical having at least one benzoxaxole
linking group represented by any one of the formulae: ##STR13##
wherein R is methyl, halo, phenyl, or phenyloxy;
R.sup.1 is a direct bond, ##STR14## arylene, oxygen, carbonyl,
sulfur, sulfinyl, or sulfonyl; m is zero, 1 or 2; and
n is zero, 1, 2 or 3.
2. The biscyclobutarene monomer of claim 1 wherein the monomer is a
bisbenzocyclobutene monomer.
3. The biscyclobutarene monomer of claim 2 wherein the benzoxazole
linkage group has the formula: ##STR15##
4. The biscyclobutarene monomer of claim 3 of the formula:
##STR16##
5. A biscyclobutarene oligomer comprising the reaction product of a
cyclobutarene-carboxylic acid, a diaminodihydroxyarene, and either
an aromatic diacid or an aromatic diacid chloride.
6. The biscyclobutarene oligomer of claim 5 wherein the
cyclobutarene-carboxylic acid is benzocyclobutene-4-carboxylic
acid.
7. The biscyclobutarene oligomer of claim 6 of the formula:
##STR17## wherein L is a benzoxazole linking group of any of the
formulae: ##STR18## and R is methyl, halo, phenyl, or phenyloxy;
R.sup.1 is a direct bond, ##STR19## arylene, oxygen, carbonyl,
sulfur, sulfinyl, or sulfonyl; m is zero, 1 or 2; and
n is zero, 1, 2 or 3;
Ar is arylene, biarylene, or two arylene moieties bridged by
oxygen, carbonyl, sulfur, sulfinyl, or sulfonyl; and
p is either zero or an integer of 1 or more.
8. The biscyclobutarene oligomer of claim 7 wherein L has the
formula: ##STR20##
9. The biscyclobutarene oligomer of claim 8 wherein Ar is
phenylene, biphenylene, or two phenylene moieties bridged by
oxygen, carbonyl, sulfur, sulfinyl or sulfonyl.
10. The biscyclobutarene oligomer of claim 9 wherein Ar is
biphenylene, or two phenylene moieties bridged by oxygen or
carbonyl.
11. The biscyclobutarene oligomer of claim 10 wherein Ar is
biphenylene.
12. The biscyclobutarene oligmer of claim 11 of the formula:
##STR21##
13. A process for preparing a polymer from the monomer of claim 1,
comprising the step of subjecting the monomer of claim 1 to ring
scission polymerization conditions.
14. A process of claim 13 wherein the polymer is a copolymer of the
monomer of claim 1 and at least a second monomer or oligomer.
15. A process of claim 14 wherein the second monomer or oligomer
has at least one cyclobutarene moiety.
16. A process of claim 15 wherein the second monomer or oligomer
has the formula: ##STR22##
17. A process for preparing a polymer from the oligomer of claim 5,
comprising the step of subjecting the oligomer of claim 5 to ring
scission polymerization conditions.
18. The process of claim 17 wherein the polymer is a copolymer of
the oligomer of claim 5 and at least a second oligomer or
monomer.
19. The process of claim 18 wherein the second oligomer or monomer
has at least one cyclobutarene moiety.
20. The process of claim 19 wherein the second monomer or oligomer
has the formula: ##STR23##
Description
BACKGROUND OF THE INVENTION
This invention relates to monomers and oligomers of
biscyclobutarenes and polymers derived therefrom. More
specifically, it relates to monomers, oligomers, and polymers of
biscyclobutarenes that are bridged by at least one benzoxazole
linkage.
Polymers derived from biscyclobutarene monomers are disclosed in
U.S. Pat. No. 4,540,763. The polymers are prepared by subjecting
biscyclobutarene monomers to temperatures sufficient for
polymerization. The polymers exhibit excellent thermal stability at
high temperatures, good chemical resistance to most industrial
solvents, good physical and mechanical properties, and low
sensitivity to water. The polymers are useful for preparing
composites, coatings and films; and as adhesives.
Although the polymers of U.S. Pat. No. 4,540,763 exhibit excellent
thermal stability at high temperatures, numerous applications in
high performance industries, such as the aerospace industry,
require polymers for advanced composites that not only exhibit high
temperature thermal stability but also exhibit high temperature
thermal stability in air for prolonged time periods. Unfortunately,
many of the polymers of U.S. Pat. No. 4,540,736 do not exhibit the
long term thermooxidative stability required for high performance
applications. The polyvalent organic and inorganic bridging groups
of the biscyclobutarenes are susceptible to oxidation reactions
when subjected to elevated temperatures for extended times.
Particularly susceptible are aliphatic bridging groups.
In view of the deficiencies of the prior art, it would be desirable
to prepare polymers derived from biscyclobutarene monomers and
oligomers that exhibit outstanding thermooxidative stability for
prolonged time periods.
SUMMARY OF THE INVENTION
In one aspect, the invention is a biscyclobutarene monomer and a
biscyclobutarene oligomer derived therefrom. The biscyclobutarene
monomer comprises two cyclobutarene moieties bridged by a divalent
radical having at least one benzoxazole linkage. The
biscyclobutarene oligomer comprises the reaction product of a
cyclobutarene-carboxylic acid, a diaminodihydroxyarene, and either
an aromatic diacid or an aromatic diacid chloride.
In another aspect, the invention comprises a process for preparing
a polymer from the biscyclobutarene monomer or the biscyclobutarene
oligomer of this invention. The process comprises the step of
subjecting the monomer or oligomer to ring scission polymerization
conditions.
The polymers derived from the biscyclobutarene monomers and the
biscyclobutarene oligomers exhibit excellent thermooxidative
stability at high temperatures for prolonged time periods. The
benzoxazole linkage of the divalent radical contributes to the
thermooxidative stability of the bridging member, and therefore the
thermooxidative stability of the polymer is enhanced. The polymers
are useful as matrix resins for advanced composites and as high
performance adhesives for bonding substrates. They are also useful
for any other application requiring service in a harsh
environment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-4 are graphs of the thermooxidative stability of polymers
derived from preferred oligomers of this invention.
DETAILED DESCRIPTION OF THE INVENTION
For purposes of describing this invention, a cyclobutarene is a
substituted or unsubstituted aromatic compound to which is fused
one or more cyclobutane rings or one or more substituted
cyclobutane rings. The aromatic ring of the cyclobutarene can be
substituted with nitro, chloro, bromo, or any other group that will
not adversely affect the thermooxidative stability of the polymers
derived from the monomers of this invention. Likewise, the
cyclobutane ring can be substituted with similar thermooxidatively
stable groups. The most preferred cyclobutarene is
benzocyclobutene.
The monomers of this invention are biscyclobutarene monomers. The
cyclobutarene moieties of the monomer are bridged by a divalent
radical that has at least one benzoxazole linkage. Processes for
preparing benzoxazole linkages within the scope of this invention
are described in U.S. Pat. No. 4,533,693, which is incorporated by
reference herein. Preferably, the benzoxazole linkage has any one
of the following formulae: ##STR1## wherein R is methyl, halo,
phenyl, or phenyloxy;
R.sup.1 is direct bond, ##STR2## arylene, oxygen, carbonyl, sulfur,
sulfinyl, or sulfonyl; m is zero, 1 or 2; and
n is zero, 1, 2 or 3.
As the term is used herein, "arylene" refers to a divalent aromatic
group. Preferred arylene is phenylene.
The most preferred benzoxazole linkage has the following formula:
##STR3##
A preferred monomer with the most preferred benzoxazole linkage is
a bisbenzocyclobutene monomer of the formula: ##STR4##
The preferred monomers can be prepared by the condensation reaction
of a cyclobutarene-carboxylic acid and a diaminodihydroxyarene at
elevated temperatures. A cyclobutarene-carboxylic acid is defined
as a cyclobutarene substituted with carboxyl, as, for example,
benzocyclobutene-4-carboxylic acid. The reaction requires a
reactive reagent that acts as a dehydrating solvent for the
condensation reaction and solubilizes the prepared monomer. One
well known reactive reagent is polyphosphoric acid. A more
preferred reagent, disclosed in Ueda et al., J. Polymer Sci.: Part
A: Polymer Chem., 24, 1019, (1986), is a mixture of methanesulfonic
acid and phosphorus pentoxide. The process conditions disclosed in
Ueda for preparing polybenzoxazole polymers are generally suitable
for preparing the monomers of this invention.
As an example of the monomer preparation, the monomer of formula 1
can be prepared by reacting 2 moles of
benzocyclobutene-4-carboxylic acid with 1 mole of
1,3-diamino-4,6-dihydroxybenzene in the presence of a sufficient
quantity of about 10 weight percent phosphorus pentoxide in
methanesulfonic acid. Enough phosphorus pentoxide should be present
so that the water of condensation is calculated to consume no more
than 15 weight percent of the phosphorus pentoxide present at the
start of the condensation reaction. The reaction mixture is stirred
under nitrogen at about 100.degree. C. for about three hours and
then cooled to room temperature. The monomer can be precipitated
from the mixture by contact with cold water and can be collected by
filtration.
In another embodiment of this invention, reactive biscyclobutarene
oligomers are prepared by reacting a cyclobutarene-carboxylic acid,
a diaminodihydroxyarene, and either an aromatic diacid or an
aromatic diacid chloride. The biscyclobutarene oligomers prepared
by this reaction are bridged by a divalent polybenzoxazole. For
purposes of describing this invention, an aromatic diacid or
aromatic diacid chloride includes diacid derivatives such as
aromatic dinitriles, diesters, diamides, imidate esters, and alkali
and akaline earth metal salts of the diacid or diacid chloride. For
example, an aromatic diester can be prepared by reacting the
corresponding diacid or diacid chloride with phenol.
The required reaction conditions are similar to the conditions
described for preparing the monomers of this invention. Preferred
biscyclobutarene oligomers are prepared from
benzocyclobutene-4-carboxylic acid and have the following formula:
##STR5## wherein L is a benzoxazole linkage of any of the formulae:
##STR6## and R is methyl, halo, phenyl, or phenyloxy; R.sup.1 is a
direct bond, ##STR7## arylene, oxygen, carbonyl, sulfur, sulfinyl,
or sulfonyl; m is zero, 1 or 2; and
n is zero, 1, 2 or 3;
Ar is arylene, biarylene, or two arylene moieties bridged by
oxygen, carbonyl, sulfur, sulfinyl, or sulfonyl; and
p is either zero or an integer of 1 or more, preferably either zero
or an integer between 1 and 1,000, inclusive.
Preferred arylene is phenylene; preferred oligomers are depicted
when Ar in the formula is phenylene, biphenylene, and two phenylene
moieties bridged by oxygen, carbonyl, sulfur, sulfinyl, or
sulfonyl. The preferred benzoxazole linkage, depicted as the letter
L in the formula, has the following formula: ##STR8##
More preferred biscyclobutarene oligomers are depicted when Ar in
the formula is either biphenylene or two phenylene moieties bridged
by oxygen or carbonyl. The most preferred biscyclobutarene oligomer
is depicted when Ar is biphenylene and the subscript n is zero, and
has the following formula: ##STR9##
The reactive biscyclobutarene oligomers exist as a mixture of
oligomers wherein the value of the subscript n for each component
of the mixture varies over a wide range. The average value of the
subscript n for an oligomer prepared by the method of this
invention is determined by the relative proportions of
cyclobutarene-carboxylic acid, diaminodihydroxyarene, and either
aromatic diacid or aromatic diacid chloride employed in the
reaction.
In another embodiment of this invention, two or more
diaminodihydroxyarenes are reacted with a cyclobutarene-carboxylic
acid and either an aromatic diacid or an aromatic diacid chloride.
A reactive biscyclobutarene oligomer having an unsymmetrical
divalent bridging member can thus be prepared. A biscyclobutarene
having an unsymmetrical bridging member may be easier to process
than a biscyclobutarene having a symmetrical bridging member
(symmetry may cause crystallization which makes the melting of the
monomer or oligomer more difficult). Similar results may be
obtained using two or more aromatic diacids or aromatic diacid
chlorides.
The biscyclobutarene monomers and reactive oligomers of this
invention can be subjected to ring scission polymerization
conditions to prepare highly crosslinked, three-dimensional
polymeric networks that are thermoxidatively stable at high
temperatures for prolonged time periods. In preferred embodiments,
the prepared polymers exhibit no more than a 10 weight percent loss
after exposure in air at 316.degree. C. for 900 hours, preferably
no more than a 10 weight percent loss after exposure in air at
343.degree. C. for 200 hours. In this context, "ring scission
polymerization" refers to the reaction of an opened cyclobutane
ring on a cyclobutarene moiety with either another opened
cyclobutane ring or a moiety capable of reacting with an opened
cyclobutane ring.
When the cyclobutane ring of the cyclobutarene moiety opens, it
forms a conjugated diene (orthoquinodimethane) that can react with
a dienophilic moiety (a "diene loving" moiety). Typically, the
opened ring reacts with another opened ring. U.S. Pat. No.
4,540,763 discloses some of the potential reactions that can occur
when opened rings react with each other. Also, an opened ring can
potentially react with an olefinic or acetylenic moiety via a
Diels-Alder reaction as disclosed in Feiser and Feiser, Organic
Chemistry, 3rd ed., 1980.
The cyclobutane ring of the cyclobutarene moiety can open by
subjecting the monomers and reactive oligomers to sufficient heat.
Typically, temperatures from about 200.degree. C. to 300.degree. C.
are sufficient to open the ring. Polymerization solvents or
catalysts are unnecessary, although a copper salt catalyst may
lower the required temperature. Gamma radiation and electron beam
radiation can also open the ring, but thermal radiation is
preferred since it can be applied by conventional methods.
The monomers and oligomers of this invention can be copolymerized
with other monomers and reactive oligomers having at least one
cyclobutarene-reactive functionality. Advantageously, the comonomer
or oligomer chosen will copolymerize with the monomers and
oligomers of this invention to form thermooxidatively stable
copolymer compositions. Preferred comonomers and oligomers are
maleimides, olefins, acetylenes, cyanates, and those having at
least one cyclobutarene moiety as described in U.S. Pat. No.
4,540,763 and copending U.S. application Ser. No. 835,013, filed
Feb. 28, 1986. An especially preferred comonomer has the following
formula: ##STR10##
This comonomer can be prepared by reacting
benzocyclobutene-4-carboxylic acid with ortho-aminophenol using
reaction conditions similar to the conditions necessary for
preparing the monomers of this invention described
hereinbefore.
The following examples illustrate but do not limit the scope of
this invention.
Example 1 Preparation of a Biscyclobutarene Oligomer With a
Divalent Bridging Member Having a Benzoxazole Linkage ##STR11##
Benzocyclobutene-4-carboxylic acid (4.70.times.10.sup.-2 moles),
4,4'-biphenyldicarboxyl chloride (2.35.times.10.sup.-2 moles),
1,3-diamino-4,6-dihydroxybenzene (4.70.times.10.sup.-2 moles), 25.0
grams (g) phosphorus pentoxide and 225 g methanesulfonic acid are
charged to a 500 milliliter (ml) resin kettle equipped with a
magnetic stirring bar and a nitrogen inlet. The mixture is stirred
in a nitrogen atmosphere and heated to 100.degree. C. After 3
hours, the reaction mixture is cooled to room temperature and is
poured into 1-liter of crushed ice to form a precipitate. The pH of
the resulting aqueous slurry is adjusted to a pH of 9 with ammonium
hydroxide. The precipitate is collected by filtration, washed
thoroughly with water, and dried in a vacuum oven at 90.degree. C.
for 8 hours to give the desired product in 95 percent yield.
EXAMPLE 2
Preparation of the Polymer from the Biscyclobutarene Oligomer of
Example 1 and the Termooxidative Stability of the Polymer and Other
polymers
A portion of the benzocyclobutene oligomer prepared from Example 1
is placed in a compression mold having a cavity shaped in the form
of a disc. The mold is heated to 160.degree. C. and sufficient
pressure is applied to make the oligomer flow completely, filling
the mold cavity. The mold is then heated under pressure to
270.degree. C. over a period of 3 hours and afterwards is allowed
to cool to room temperature while pressure is maintained. After
cooling to room temperature, the mold is opened to reveal a solid
polymer disc conforming to the shape of the mold cavity. The
polymer disc is removed from the mold and is placed in a
circulating air oven at 316.degree. C. (600.degree. F.). The disc
is removed from the oven at varying times and is weighed to measure
the isothermal weight loss of the polymer. After each measurement,
the polymer is returned to the oven.
Another portion of the oligomer prepared from Example 1 is
similarly polymerized in the compression mold and the resulting
polymer is placed in the circulating air oven at 343.degree. C.
(650.degree. F.). Again, the polymer disc is removed from the oven
at varying times and is weighed to measure the isothermal weight
loss.
The resulting isothermal weight loss measurements at each
temperature are presented in FIGS. 1 and 2.
The results at 316.degree. C. indicate that over 90 percent of the
weight of the polymer remains after exposure in air for more than
900 hours. The results at 343.degree. C. indicate that about 90
percent of the weight of the polymer remains after exposure in air
for more than 200 hours. These results indicate that a
biscyclobutarene oligomer having a divalent bridging member with
benzoxazole linkages exhibits outstanding thermoxidative stability
at high temperatures for prolonged time periods.
The procedure of Example 1 is used to prepare a biscyclobutarene
oligomer of the formula: ##STR12##
The biscyclobutarene is polymerized and analyzed for
thermooxidative stability at 316.degree. C. and 343.degree. C.
using the procedure described in this example. The resulting
isothermal weight loss measurements at each temperature are
presented in FIGS. 3 and 4.
Again, the results at both temperatures indicate outstanding
thermooxidative stability at high temperatures for prolonged time
periods.
Upon repeating the procedures of Examples 1 and 2 with other
oligomers and monomers of this invention, similar outstanding
results are obtained.
* * * * *